This invention relates to superconductors, and has particular reference to intermetallic superconductors.
It has been proposed to manufacture superconductors of intermetallic compounds such as Nb.sub.3 Sn. Unfortunately, such compounds are very brittle, and tend to break when subjected to strain. Consequently, proposals have been made to manufacture a precursor structure comprising niobium and tin, or the other components of the eventual intermetallic superconductor in the unreacted state on a support. The precursor is then manufactured into a solenoid, and the solenoid heated to a temperature sufficiently high to cause a reaction between the components to form the intermetallic compound. This causes problems, in that the whole solenoid has to be heated, which is obviously inconvenient, since, for example, distortion of the winding can occur. Also, the resultant structure is fragile, and the high loads imposed on it, as a result of the magnetic fields produced, during use, can cause sufficient strain to lead to breakage of the intermetallic compound.
Superconducting composites including filamentary intermetallic compounds in which the intermetallic compound is reacted prior to the winding of the solenoid offer advantages in terms of handling and uniformity of superconducting properties, but would be unsatisfactory if the composite structure was too brittle.
As a result of observations of a large number of different structures, it has unexpectedly been found that the degree of apparent brittleness in composite intermetallic superconductors can be reduced by particular physical arrangements of the component parts of the composite.